Compare-StringSet.ps1

Compare-StringSet.ps1

using namespace System.Collections.Generic

function Compare-StringSet {
    <#
    .synopsis
        quickly
    .example
        Compare-StringSet ('a'..'g') ('c'..'z')
        Compare-StringSet ('a'..'g') ('A'..'E')
    .example
        Compare-StringSet ('a'..'g') ('A'..'E') -Insensitive
    .LINK
        https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.hashset-1?view=net-6.0#hashset-and-linq-set-operations

    .NOTES
        other functions:
            .ctor, Add, Clear, Comparer, Contains, CopyTo, Count, CreateSetComparer, EnsureCapacity, Enumerator, ExceptWith, GetEnumerator, GetObjectData, IntersectWith, IsProperSubsetOf, IsProperSupersetOf, IsSubsetOf, IsSupersetOf, OnDeserialization, Overlaps, Remove, RemoveWhere, SetEquals, SymmetricExceptWith, TrimExcess, TryGetValue, UnionWith
    #>
    [Alias(
        'Set->CompareString'
    )]
    param(
        [string[]]$ListA,
        [string[]]$ListB,

        [switch]$Insensitive
    )
    if($Insensitive) { throw "NYI: Equality comparison"}
    <#
    todo: future:
        When empty column format string as '∅'
        intersect as ..
        union ∪
        '∉' etc
    #>
    class StringSetComparisonResult {
        [list[string]]$Intersect
        [list[string]]$RemainingLeft
        [list[string]]$RemainingRight
        [list[string]]$Union
    }

    $results = [ordered]@{}
    $SetA = [HashSet[string]]::new( [string[]]$ListA)
    $SetB = [HashSet[string]]::new( [string[]]$ListB)

    $SetA.IntersectWith( $setB )
    $results['Intersect'] = $SetA

    $SetA = [HashSet[string]]::new( [string[]]$ListA)
    $SetB = [HashSet[string]]::new( [string[]]$ListB)

    # $SetA -notin $results.Intersect
    $results.'RemainingLeft' =  $SetA | ?{
        $results.'Intersect' -notcontains $_
    }
    $results.'RemainingRight' =  $SetB | ?{
        $results.'Intersect' -notcontains $_
    }

    $SetA = [HashSet[string]]::new( [string[]]$ListA)
    $SetB = [HashSet[string]]::new( [string[]]$ListB)

    $SetA.UnionWith( $SetB )
    $results.'Union' = $SetA
    
    [StringSetComparisonResult]$Results
    # [hashset[string]]::new( [string[]]('a', 'b')
}